Ignition system



April 4, 1967 0. K. NILSSEN I 3,312,210

IGNITION SYSTEM Filed Oct. 12, 1964 5 Sheets-Sheet 1 FIG 2 OLE K. NILSSEN lNl/E/VTOR v (\l 2 i Z i/ ATTORNEYS April 4, 1967 0. K. NILSSEN IGNITION SYSTEM 3 Sheecs$heet 2 Filed Oct. 12, 1964 OLE K. NILSSEN I INVENTOR I ,4 r TORNEYS April 4, 1 967 ,0 K. NILSSEN IGNITION SYSTEM 3 Sheets-Sheet 5 Filed Oct. 12, 1954 FIG.6

OLE K. NILSSEN INVENTOR F IG 7 United States Patent 9 ice- 3,312,210 IGNITIONSYSTEM Ole K. Nilssen, Livonia, Mich., assignor to Ford Motor Company, Dearborn, Mich.,,a corporation of Delaware Filed Oct. 12, 1 964, Ser. No. 403,263

4 Claims. (Cl. 123-148) This invention 7 relates to anignition system for an internal combustion engine, and more particularly to an ignition system employing a solid stateswitching system that provides a substantially constant charging time for the ignition coil of the ignition system.

In view of the ever increasing emphasis on long term reliability in automotive vehicles, the area of ignition is especially important. While it is highly desirable to have an ignition system that remains trouble free without maintenance for approximately 100,000 miles, the conventional system currently used falls far short of this goal. In addition to a short life expectancy of approximately 10,000 miles, it has other limitations. Among these are a notable reduction in ignition power at high engine speeds; low electrical efficiency, especially at low engine speeds; insufiicient power reserve for firing part-ially fouled plugs; and finally, undesirably large current drain at stall. This latter limitation means that the components in the ignition system must be designed for much higher dissipations than otherwise necessary.

There have been many attempts to solve the problems created by the conventional ignition system. A number of systems that solve one or more of these problems have been developed. It is believed, however, that none approaches providing a solution to all of the problems, although most of the transistorized or solid state switching ignition systems do provide significantly improved'reliability.

In certain transistorized ignition systems, the life expectancy of the ignition system and the ignition performance at high engine speeds have been improved, but this has often been done at the expense of a significant increase in an average current consumption. In most ignition systems, including transistorized ignition systems known today, the current through the primary winding of the ignition coil reaches the desired level much sooner than necessary at low speeds, while at high speeds there is nmufiicient time for proper buildup of current in the primary winding.

The present invention provides an improvement over the conventional ignition systems and known transistorized ignition systems in that it provides a substantially constant charging time for the primary winding of the ignition coil independent of engine speed. This constant charging time is long enough to charge the primary winding sufliciently at all engine speeds to provide for proper development of ignition voltages in the secondary wind-ing of the ignition coil. This is done by a substantial direct connection of the battery or source of electrical energy of the vehicle to the primary winding without using a series resistor for a short constant period of time directly before the ignition voltages are required by the ignition system. As a result, the ignition system of the present invention provides low current drain at stall (on the order of A of an amp), high electrical efliciency (drawing only of an amp at idle), no loss in performance at high engine speeds,-

a-nd much reduced power dissipation requirements of the ignition coil, the solid state switching device employed, and the other components of the ignition system.

In the present invention, a solid state switching device or transistor is employed to control-the energization of the primary winding of the ignition coil from the source of electrical energy or battery of the vehicle. The switching of the solid state switching device or transistor is 3,3 10 Patented Apr; 4, 1967 under the control'of a saturable switching core. This saturable sw-itc-hing' core is normally; biased toward one state of saturation through a circuit that maybe periodically interrupted or which periodically reduces this .bias n synchronism' with the operation of the engine. .fThe interruption of this circuit or thereduction of .the bias switches the solidstate switching device intoii-ts conducting state. This switching device is coupled to the, saturable switching core in a positive feedback arrangement so that the conduction of the solid state switching device or transistor drives the saturable switching core into its saturated condition in the other direct-ion -When the core reaches this saturated condition, the feedback is insufficient to maintain conduction of the solid state switching device or transistor and this device or transistor ceases conduction thereby de-energizingthe primary winding of the ignition coil and generating igni-ti-on'voltages in the secondary winding of the ignition coil. i

When the circuit connection that biases the saturable or switched back to its original state for the commencement of another cycle of ignition operation,

The saturable switching core maybe automatically reset to the original state of saturationby the voltage developed across the primary winding of the ignitioncoil when the solid state switching device or transistordeenergizes this primary winding; As a result, repetitive sparking may result from this system. This may be desirable in certain cases, particularly in starting, but in other cases it has disadvantages. If it is desired to prevent repetitive sparking, circuit means are coupled to the primary winding of the ignition coil and the saturable switching core to prevent the resetting of the saturableswitching core by the voltage developed in the primary winding of the ignition coil. This may take the form of a diode or unidirectional current device that prevents this voltage or the current developed thereby from appearing or flowing through any of the windings of the saturable'gsw itching core or which directs this electrical energy into the windings in such a way that the magnetizing etiect s of energizing the windings are counter-balanced to leave little net magnetizing eifect in the saturable switching core... The. saturable switching core must, therefore, be reset by the initiation of the next ignition cycle in which the normal bias on the switching. core is established. This arrangement will prevent, therefore, the repetitive sparking and provide one shot oper ati on of the system for the firing of each spark plugm In order to provide a constant in the battery voltage of the automotive vehicle, the parameters of the biasing circuit for the saturable switching core may beselected so that the core is not biased into its fully saturatedscondition. It can be shown that the time necessary to saturate the core is inversely proportional to the battery voltage and directly proportional to the flux increment through which the core is switched. This arrangement will compensate automatically for any changes in battery voltage, since if the battery voltage increases, the bias on the saturable switch-ing core will increase and the increment of flux through which the core must be switched will also increase proportionally. On the other hand, the reverse situation will prevail should the battery voltage decrease over its normal value. This arrangement thus provides for a constant switching time I charging time ofjthl primary winding of the ignition coil despite variability ciency, good performance at high engine speeds, and reduced power dissipation requirements of the coil and other components in the ignition system.

Another object of the invention is the provision of an uncomplicated, reliable ignition system for an internal combustion engine in 'which a constant charging time for the ignition coil is provided independent of engine speed.

A further object of the invention is the provision of an ignition system for an internal combustion engine in which the ignition coil is charged for only a short constant time period immediately prior to the generation of the ignition voltages with this short constant time period being independent of engine speed.

Other objects and attendant advantages of the present invention will be more readily apparent as the specification is considered in connection with the attached dra wing in which:

FIGURE 1 is a schematic electrical diagram of one embodiment of the invention;

FIGURE 2 is a hysteresis loop of the saturable switching core of the embodiment of FIGURE 1;

FIGURE 3 is a modification of the circuit of FIGURE 1 that will prevent repetitive oscillations or sparking that might otherwise occur with the system of FIGURE 1;

FIGURE 4 is a schematic electrical diagram of another embodiment of the invention;

FIGURE 5 is a partial schematic electrical diagram of another embodiment of the invention similar to that of FIGURE 4 with the distributor not shown;

FIGURE 6 is a partial schematic electrical diagram of still another embodiment of the invention with the distributor of the ignition system not shown;

FIGURE 7 is a schematic electrical diagram of another embodiment of the invention, and

FIGURE 8 is a hysteresis loop of the saturable switching core that may be used with the embodiment of the invention shown in FIGURE 7 or any of the other embodiments of the invention.

Referring now to the drawings in which like reference numerals designate like parts throughout the several views thereof, there is shown in FIGURE 1 a schematic electrical diagram of one embodiment of the invention in which an ignition coil 10 has a primary winding 11 and a secondary winding 12. The secondary winding 12 is connected through lead 13 to a rotating arm 14 of a distributor 16. This rotating arm 14 sequentially connects a plurality of spark plugs 17 to the secondary winding 12 of the ignition coil 10 through the lead 13 and leads 18, 19, 20, 21, 22 and 23.

The primary winding 11 of the ignition coil 10 is connected to the negative terminal 26 of a source of electrical energy or storage battery 27 through leads 28 and 31. The other terminal of the primary winding 11 of ignition coil 10 is connected to an output electrode 32, in the form of a collector, of a solid state switching device preferably in the form of transistor 33. The other output electrode 34 of this solid state switching device or transistor 33, shown in the form of an emitter, is connected to the positive terminal 35 of the source of electrical energy or battery 27 through lead 36, lead '37 and lead 38.

A saturable switching core 41 having the hysteresis loop schematically represented in FIGURE 2, is employed to control the conduction of the solid state switching device or transistor 33. This saturable switching core has a first winding 42 having its dot marked terminal connected to the positive terminal 35 of battery 27 through lead 43, resistor 44, lead 40, lead 37 and lead 36. The other end of the winding 42 is connected through lead 45, with contact 46 of ignition contact breaker points 47. The other contact 48 is connected to lead 31 through a movable arm 51. The ignition contact breaker points 47 are normally biased to a closed position, and are separated or opened periodically by a cam 54 that operates a follower 55 coupled to the arm 51. This cam is operated in synchronism with the rotatable arm 14 of the distributor 16 as shown by the dotted line 56, and it is arranged so that the ignition cont-act breaker points 47 open just shortly before the rotating arm 14 makes contact with the leads 18 hrough 23 respectively of the distributor 16.

The saturable switching core 41 also has a second winding 61 wound thereon that has its dot marked terminal coupled to lead 31 via lead 62 and the other end connected through lead 63 to the ignition coil 10 and the output electrode or collector 32 of the solid state switching device or transistor 33. It can be appreciated, therefore, that the winding 61 is connected directly across the primary winding 11 of ignition coil 10, and is connected in parallel with the primary winding 11 in relation to current flow through the solid state switching device or transistor 33. A third winding 65- in the form of a feedback winding has its dot marked terminal connected through lead 66 to a control electrode or base 67 of the solid state switching device or transistor 33, while the other end of the winding 65 is connected through lead 68, resistor 71, lead 72, lead 37, and lead 38 to the output or emitter electrode 34 of the solid state switching device or transistor 33.

A capacitor 73 is connected across the primary winding 11 of ignition coil 10 for the usual purposes of preventing too rapid a rise in the voltage in the primary winding 11 as the solid state switching device or transistor 33 is de-energized. This furnishes protection for the transistor against reverse voltages that may be so high as to destroy its operating characteristics.

In operation of the circuit shown inFIGURE 1, with the contacts 46 and 48 of the ignition contact breaker points 47 closed, a circuit will be established through the first winding 42 on the saturable switching core 41 from the source ofelectrical energy or battery 27. The resistance of this circuit, including the resistance of resistor 44 and the resistance of the winding 42, is such that the number of ampere turns or volt seconds applied to the core 41 is such to bias it into a negative state of saturation as designated by the letter A in FIGURE 2. At this time, the solid state switching device or transistor 33 will be in a nonconducting state because no voltage will be developed at thistime across the feedback winding 65, and the emitter 34 and the base 67 will be at the same potential. Since the solid state switching device 33 is in the nonconducting state, there willbe no current flow through the primary winding 11 of theignition coil 10 nor through the winding 61 of the saturable switching core 41.

It should be noted that with the dot convention employed here, current into a dot marked terminal will produce a magnetizing force to drive the core toward a negative state of saturation (point A) while current into an unmarked terminal willproduce a magnetizing force to drive the core toward a positive state of saturation (point C). Similarly, a flux change from a negative flux state toward a positive flux state will produce a negative voltage at a dot marked terminal of a winding with respect to its unmarked terminal and a flux change from a positive flux state toward a negative flux state will produce a positive voltage at a dot marked terminal of a winding with respect to its unmarked terminal.

When the ignition contact breaker points 47 open under the action of the cam 54 and follower 55, the bias on the saturable switching core will be removed and the flux level will fall to the remnant flux level at B. This changing flux will induce in the feedback winding 65 a negative potential at the dot with respect to the potential at the other end of the winding 65. This will turn the transistor to a conducting state, and provide current flow through the primary winding 11 of the ignition coil 10 and through the winding 61 connected in parallel with the primary winding 11. Since current flows into the unmarked terminal of winding 61, the core will be switched toward a positive state of saturation and a negative potential will be produced at the dot marked terminal with respect to the unmarked terminal of feedback winding 65, thereby turning the transistor to its fully conducting state by virtue of this feedback action. Current through winding 61 provides sufiicient magnetizing force on the saturable switching core 41 to drive it from point B into a saturated condition at point C.

When the saturable switching core reaches the saturated state at point C, the feedback voltage in the winding 65 will fall to zero thereby turning off the transistor or solid state switching device 33 and interrupting the current flow through the primary winding 11 of ignition coil 10. This interruption of the current flow will induce a voltage in the primary winding 11 and a stepped up ignition voltage in the secondary winding 12 which will be applied at this time to one of the spark plugs through the lead 13, the rotatable arm 14, and one of the leads 18 through 23 of the distributor 16. This voltage will also act on the winding 61 to reset the core back to the point A since the voltage across the primary winding 11 has reversed so that a positive potential appears at the dot marked terminal of the winding 61. A positive potential will also be present at the dot marked terminal of feedback winding 65 thereby keeping the solid state switching device of transistor 33 in the cutofi condition. It can be appreciated that when the voltage across the primary winding 11 of ignition coil decays, the saturable switching core 41 will again fall to point B on the hysteresis loop shown in FIGURE 2 and the cycle will repeat as long as the ignition contact breaker points 47 remain open thereby generating a repetitive sparking action to be applied to the spark plugs 17.

The partial circuit diagram in FIGURE 3 discloses a diode 75 positioned in the lead 62. The eifect of this diode is to prevent the saturable switching core 41 from being fully reset by the ignition voltage as it appears across the primary winding 11 of the ignition coil 10 since it prevents current flow into the dot marked terminal of the winding 61 that would have the effect of resetting the core back to point A in FIGURE 2. Thus, rather than being moved down to the point A in FIGURE 2, which is an unstable position when the ignition contact breaker points 47 are open, the magnetization of the core will now fall only to point D which is a stable position of residual flux. As soon as the contacts 46 and 4810f the ignition contact breaker points 47 close, the magnetization of the core will be switched back to point A and another ignition cycle will occur only when the contacts 46 and 48 of the ignition contact breaker points 47 open.

Another embodiment of the ignition system of this invention is shown in FIGURE 4. This embodiment employs essentially the same components and operates in much the same way as the embodiments disclosed in FIGURES l and 2. In this embodiment, however, the primary winding 11 of the ignition coil 10 is connected to the positive terminal of the source of electrical energy or battery 27 through lead 36 and lead 81. The winding 61 on the saturable switching core 41 is connected in series with the primary winding 11 of ignition coil 10 rather than being connected in parallel with it. This is accomplished by connecting the lead 62 from the winding 61 to the ignition coil 10 through lead 8-2. The other lead 63 from the winding 61 is connected to a lead 83 that is in turn connected to the output electrode or emitter 34 of the solid state switch or transistor 33 through lead 84, diode 85 and lead 86. The other output electrode or collector 32 of the solid state switching device or transistor 33 is connected to the negative terminal 26 of the source of electrical energy or battery 27 through a lead 87, lead 31, and lead 28.

The capacitor 73 is this embodiment is connected between the lead 40 and a lead 91 that connects the lead 82 with the lead 31. This capaciton'therefore, is connected directly across the primary winding 11 of ignition coil 10. The lead 91 has a diode 92 positioned therein to permit current flow from the lead 31 and the negative the ignition coil 10. In addition, the resistor 71 rather than being connected in series with the winding 65 on the saturable switching core 41 is connected in parallel therewith by being connected to the base 67 of the solid state switching device or transistor 33 through lead 68 and by being connected to the lead 83 by means of lead 72.

The embodiment of the ignition system shown in FIGURE 5 is very similar to that shown in FIGURE 4 except that a diode 92 rather than being connected in the lead 91 between leads 31 and 82, is connected directly in the lead 82 and in series with the primary winding 11 of ignition coil 10 and the winding 61 on the saturable switching core 41. In addition, the capacitor 73 rather than being connected directly across the ignition coil 11 is connected from the terminal of the primary winding 11 of the ignition coil adjacent the diode 92 to the lead 31 that is in turn connected to the negative terminal 26 of the source of electrical energy or storage battery 27. It should be noted in connection with FIGURE 5 that the distributor 16 has not been shown in the interest of brevity.

The embodiment of the ignition system of the invention shown in FIGURE 6 is similar to that shown in FIGURE 4 except that a pair of resistors 96 and 97 are positioned in series with the winding 42. A switch 98 is connected across the resistor 97 to permit this resistor to be shorted out during starting operations. The diode 92 rather than being connected between the lead 31 and the lead 82 via lead 91 is connected to the base 67 of the solid state switching device or transistor 33 through a lead 101, and to the lead 82 which is connected to one sideof the primary windingll of ignition coil 10 via lead 102. This diode is pole-d to prevent current flow from the primary winding 11 of ignition coil 10 to the base67, but permits current to flow from the base 67 to the lead 82 for purposes to be described subsequently. Inthis system, a capacitor 103 is shown connected across the ignition breaker points 47 to aid in suppressing arcing of thecontacts 46 and 48 as they open. It is to be understood that such a capacitor could also be used in any of the other embodiments shown and described.

FIGURE 7 shows another embodiment of the ignition system of the invention in which the primary winding 11 of the ignition coil 10 is connected to the collector or output electrode 32 of the solid state switching device or transistor 33 via a lead 105. The capacitor 73 is shown connected between a junction 1116 and lead 37 so that it is connected across the solid state switching device or transistor 33 and the winding 61 for protective purposes. A diode 92 in this embodiment of the invention is connected between the junction 196 that is connected directly to one side of the primary winding 11 and to the unmarked terminal of the winding 42 via junction 107.

The operation of the embodiment of the invention shown in FIGURE 4 is substantially the same as that shown in FIGURE 1. When the ignition contact breaker points 47 close, the saturable switching core 41 is biased into negative saturation shown by the letter A on the hysteresis loop of FIGURE 2. When the ignition contact breaker points open, the magnetization of the core will drop to point B thereby causing an output pulse to be generated in the feedback winding 65 and turning the solid state switching device or transistor 33 to its conducting state. The current through the primary winding 11 and the solid state switching device or transistor 33 also flows through the winding 61 causing a positive feedback to the winding 65 thereby rapidly bringing the solid state switching device or transistor 33 to its fully conducting state. The electrical energy in the winding 61 drives the solid saturable switching core 41 to its positive saturated state at point C. At this time the feedback voltage on the winding 65 disappears and the transistor or solid state switching device 33 is brought to its nonconducting state. This de-energizes the primary winding 11 of the ignition coil thereby generating high ignition voltages in the secondary winding 12.

The diode 92 positioned in the lead 91 between lead 31 and lead 82 is employed to prevent the voltages present at the primary winding 11 of ignition coil 10 from resetting the saturable switching core 41. If the junction of leads 91 and 82 should go negative during the ignition cycle with respect to ground, which is quite likely to 'occur, current fiows directly through the diode 92 and clamps this side of the ignition coil to ground voltage or potential. If this diode were not present and the junction "of leads 82 and 91 should go negative with respect to ground, current could flow from ground to this junction through the collector 32 and base 67 of the solid state switching device or transistor 33 through the winding 65 and then through the winding 61 which would reset the core back to the point A in the hysteresis loop shown in FIGURE 2. This action would cause repetitive sparking or ignition voltages to be generated in the secondary winding 12 as long as the ignition contact breaker points 47 were open. The diode 85 also is an aid to prevent spurious oscillations. It provides a reverse bias between the base 67 or control electrode and the output electrode or emitter 34 of the solid state switching device or transistor 33 which will prevent transient voltages from initiating another ignition cycle.

The operation of the embodiments of the ignition systern shown in FIGURES 5, 6 and 7, is very similar to that described in relation to FIGURE 4 with certain exceptions as will now be discussed. In FIGURE 5, the diode 92 rather than being positioned across or in a shunt relationship with respect to the windings 65 and 61 to prevent resetting of the saturable switching core 41, is positioned in series with the two windings 65 and 61. Thus, if for any reason the side of the primary winding 11 of ignition coil 10 connected to the diode 92 should go negative with respect to ground, the diode is poled to prevent current flow from ground through the solid state switching device or transistor 33, the winding 65 and the winding 61 as previously discussed in relation to FIGURE 4.

In FIGURE 6, the diode 92 is connected between ,the base or control electrode 67 of solid state switching device or transistor 33 and the lead 82. This provides a shunt path for current flow from ground through the collector-base circuit of the solid state switching device or transistor 33 should the side of the ignition coil 10 connected to lead 82 go negative with respect to ground for any reason during the ignition cycle. Thus, current will not flow through the windings 65 and 61 in this event, and the saturable switching core 41 will not be reset until the ignition contact breaker points 47 close.

In FIGURE 7, the diode 92 is connected between the end of the primary winding 11 of the ignition coil 10 connected to lead 105 and the junction 107 at the unmarked terminal of the winding 42. In this case, the number of turns in the winding 42 should be greater than or equal to the sum of the turns in windings 65 and 61, and the resistance of the circuit coupling junction 106 to the junction of leads 37 and 40 through diode 92 and winding 43 should be equal to or smaller than the resistance of the circuit connecting these two junctions through the diode formed by the collector base junction of transistor or solid state switching device 33 and the windings 61 and 65. It can be appreciated, therefore, in this 'case that if the side of the primary Winding 11 of ignition coil 10 connected to the lead 105 should go positive with respect to the positive terminal 35 of the source of electrical energy or storage battery 27, current could flow through the collector-base circuit of the solid state switching device or transistor 33 and through the windings 65 and 61 and that current could also flow through the diode 92 and through the winding 42. Since current would be flowing into the winding 42 to magnetize the core in the opposite direction to the current through the windings 65 and 61 and with the establishment of the relationship of the turns and resistances in these windings and circuits as stated above, the magnetizing effect of these two currents would cancel each other and the core would not be reset during the ignition cycle until the ignition contact breaker points 47 close.

It can be shown that the amount of time that it takes to saturate the saturable switching core 41 from any given level of magnetization into the saturated state is dependent upon the battery voltage 27. More specifically, this time is proportional to the increment of flux through which the saturable switching core is to be switched and inversely proportional to the voltage of the source of electrical energy 27. In the embodiment of the invention shown in FIGURE 6, the resistances 96 and 97 are established such that the magnetizing effect of the electrical energy in the winding 42 when the contact ignition breaker points are closed, will position the core at a negative flux level between the zero flux level and a saturated flux level, for example, at the point F as shown in FIG- URE 8. This setting of the saturable switching core 41 in the intermediate flux level position will provide a constant time between the opening of the breaker points and the saturation of the core, and hence a constant energization time of the primary winding 11 of the ignition coil 10. As stated previously, the time for bringing the saturable switching core into a state of saturation is proportional to the increment of flux through which the core is switched and is inversely proportional to the voltage of the battery 27. Hence any increase in the battery voltage 27 will automatically move the point F further down towards a negative state of saturation in proportion to this voltage increase thereby increasing the increment of flux through which the core is switched in proportion to the increased battery voltage. These two effects will offset or cancel each other, hence providing automatic compensation for changes in battery voltage and providing a constant charging time for the primary winding of the ignition 10 independent of changes in battery voltage.

The automatic compensation for changes in battery voltage to maintain a constant charging time for the primary winding of the ignition can also be accomplished in any of the other embodiments of the invention shown by adjusting the resistance in the circuit containing the winding 42 and the ignition contact breaker points 47 so that the saturable switching core 41 is normally biased to an intermediate flux level as shown at F in FIGURE 8. For example, it may be readily accomplished by adjustment of the variable resistor 44 shown in FIGURE 4. It should be noted here that the hysteresis loop of the saturable switching co-re should have an appreciable slope to provide a stable operating point as at F when automatic compensation of charging time is desired.

This automatic compensation for the change of battery voltage to maintain a constant charging time for the primary winding 11 of the ignition coil 10 maintains proper timing of the generation of ignition voltages, since these voltages are generated at the time the saturable switching core 41 saturates.

In the embodiment shown in FIGURE 6, the switch 98 may be closed during starting operations so that only the resistor 96 is in series with the Winding 42. This will increase the charging time for the primary winding 11 of the ignition coil 10 during starting operations since the operating point P in FIGURE 8 will be moved further down toward the negative state of saturation thereby increasing the increment of flux through which the core is switched as it is switched to its positive state of saturation.

It should be noted that in all of the embodiments of the invention the primary winding 11 01': the ignition coil 10 is directly connected to the battery 27 through the solid state switching device or transistor 33 with no limiting resistors being placed in series with this clrcuit. The only resistance is that of the primary winding itself, the small -resistance of the winding 61 on the core 41 in the case of the embodiment of FIGURES 4 through 7, and the forward resistance of the solid state switching device or transistor 33. Thus, by this direct connection for the short constant time period, the primary winding 11 of ignition coil 10 may be charged to proper levels by the saturable transformer operating to turn on the solid state switching device or transistor 33 for the short constant time period immediately prior to the generation of the ignition voltages in the ignition coil. It should be noted that in all of these embodiments of the invention, that the charging of the ignition coil 10 is initiated by the opening of the contacts 46 and 48 of the ignition contact breaker points 47, and that ignition voltages will be generated in the ignition coil 10 a short constant time period thereafter, depending upon the time necessary to saturate the saturable switching core 41.

A typical example of the components used in this ignition system is given here by way of example only in reference to the ignition system disclosed by FIGURE 6:

The iginition coil 10 is conventional except that the primary winding employs approximately 75 turns rather than the usual 250.

Solid state switching device or transistor 33 is an RCA 1906 transistor with a collector-emitter break-down voltage (with reversely biased base-emitter junction) of 170 volts. Its current gain should be 10 at an 1 :16 amp.

Saturable switching core 41 is a Silectron core made of cut 6 mil laminations. Its cross sectional area is 0.2 cm?. Its magnetic path is 4 cm. The winding 4280 turns of #32 wire, winding 61-4 turns of #18 wire, and winding 6540 turns of #28 wire.

Resistor 96 is a 2782/1 w. resistor and resistor 97 is a 2709/ 0.5 w. resistor.

Capacitor 73 has a value of ,uf./200 volts paper capacitor.

Diode 92 is a General Electric 1N92.

Capacitor 103 has a value of 0.1 it/20 volts.

The present invention provides an ignition system in which the primary winding of the ignition cOil is charged only for a short constant time period immediately prior to sparking. This constant charging time provides low current drain at stall and high electrical efficiency. No loss of performance at high engine speeds is experienced, since the amount of time necessary to charge the primary winding is so short, typically 1 millisecond, that even during very high speed operation sufiicient time is provided between ignition cycles to fully complete the charging of the ignition coil. Also, the power dissipation requirements of the components in the system can be substantially reduced over prior known systems.

It is to be understood that this invention is not to be limited to the exact construction shown and described, but that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. An ignition system for an internal combustion engine comprising, a source of electrical energy, an ignition coil including a primary winding and a secondary winding, a plurality of spark plugs, means operable in synchronism with the engine for sequentially coupling said spark plugs to the secondary winding of said ignition coil, a solid state switching device including an output circuit and an input circuit, a saturable switching core capable of being saturated in a first or a second saturable state, a first winding coupled to said source of electrical energy and wound on said saturable core to bias said saturable switching core toward said first saturable state, a second Winding coupling said source of electrical energy, said output circuit of said solid state switching device and said primary winding of said ignition coil and wound on said core in a direction to drive said saturable switching core into said second state of saturation, a third winding wound on said saturable core and positioned in the input circuit of said solid state switching device, said third winding wound in a positive feedback direction with respect to said second winding, and means operable in synchronism with said first mentioned means for periodically interrupting the coupling between said first winding and said source of electrical energy whereby said solid state switching device is switched to its conducting state by the energy induced in said third winding and is maintained in its conductive state until said saturable switching core saturates in said second direction whereby said primary winding of said ignition coil is energized only during the period between the interruption of the coupling between said first winding and said source of electrical energy and the saturation of said saturable switching core in said second direction which period is substantially constant and independent of engine speed.

2. An ignition system for an internal combustion engine comprising, a source of electrical energy, an ignition coil including a primary winding and a secondary winding, a spark plug, means operable in synchronism with the engine for coupling and decoupling said secondary Winding to and from said spark plug, and means coupling said primary winding and said source of electrical energy for charging said primary winding from said source of electrical energy for a short constant time period irrespective of engine speed immediately prior to the requirement for ignition voltages in said secondary winding of said ignition coil, said second coupling means including a transistor, a saturable switching core and an inductive coupling therebetween to switch said transistor, circuit means inductively coupled to said saturable switching core and said source of electrical energy for biasing said saturable switching core toward one state of saturation, signal means coupled to said circuit means and operable in timed synchronisrh with the engine and said first mentioned means for removing the bias from said saturable switching core, and circuit means coupling said source of electrical energy, said saturable switching core and said transistor for driving said saturable switching core to the other state of saturation by inductive action when said signal means removes the bias from said saturable switching transformer and for switching said transistor to a conducting state only during the period between the removal of said bias from said saturable switching core and the saturation of said saturable switching core.

3. An ignition system for an internal combustion engine comprising, a source of electrical energy, an ignition coil comprising a primary and a secondary winding, a spark plug, means operable in synchronism with the engine for coupling and decoupling said spark plug with said secondary winding, a saturable switching core, means inductively coupled to said saturable switching core and said source of electrical energy for biasing said saturable switching core to a flux level in one direction intermediate a zero flux level and a saturation flux level, means operable in timed synchronism with said engine and with said first mentioned means and coupled to said second mentioned means for periodically reducing the bias applied to said saturable switching core by said second mentioned means, a transistor switch, and circuit means coupling said transistor switch, said primary winding of said ignition coil, said saturable switching core and said source of electrical energy for switching said transistor switch into a conducting state, energizing said primary winding and driving saturable switching core into a saturated condition in the other direction of magnetization when said third mentioned means reduces the bias on said saturable switching core, said circuit means including means for causing said transistor switch to be switched to its nonconducting state and said primary winding to therefore be de-energized when said saturable switching core reaches said saturated condition.

4. In an ignition system for an internal combustion engine, a source of electrical energy, an ignition coil including a primary winding and a secondary winding,.a spark plug, means operable in timed synchronism with the engine for periodically coupling and decoupling said secondary winding of said ignition coil with said spark plug, a saturable switching core, means coupling said saturable switching core and said source of electrical energy for biasing said saturable switching core toward one of its saturated states, switching means operable in timed synchronisrn with said first mentioned means and the engine for periodically reducing the bias, a transistor switch, circuit means coupling said primary winding of said ignition coil, said source of electrical energy, said transistor switch and saturable switching core for turning on said transistor switch, energizing said primary winding of said ignition coil and driving said saturable switching core into the other state of saturation when said switching means reduces the bias on said saturable switching core, said circuit means including means for switching said transistor switch to a nonconducting state when said saturable switching core becomes saturated whereby said primary winding of said ignition coil is de-energized, and means coupled in circuit with said primary winding of said ignition coil and said saturable switching core for preventing the voltages generated in said primary winding from resetting said saturable switching core.

References Cited by the Examiner UNITED STATES PATENTS MARK NEWMAN, Primary Examiner.

LAURENCE M. GOODRIDGE, Examiner. 

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE COMPRISING, A SOURCE OF ELECTRICAL ENERGY, AN IGNITION COIL INCLUDING A PRIMARY WINDING AND A SECONDARY WINDING, A PLURALITY OF SPARK PLUGS, MEANS OPERABLE IN SYNCHRONISM WITH THE ENGINE FOR SEQUENTIALLY COUPLING SAID SPARK PLUGS TO THE SECONDARY WINDING OF SAID IGNITION COIL, A SOLID STATE SWITCHING DEVICE INCLUDING AN OUTPUT CIRCUIT AND AN INPUT CIRCUIT, A SATURABLE SWITCHING CORE CAPABLE OF BEING SATURATED IN A FIRST OR A SECOND SATURABLE STATE, A FIRST WINDING COUPLED TO SAID SOURCE OF ELECTRICAL ENERGY AND WOUND ON SAID SATURABLE CORE TO BIAS SAID SATURABLE SWITCHING CORE TOWARD SAID FIRST SATURABLE STATE, A SECOND WINDING COUPLING SAID SOURCE OF ELECTRICAL ENERGY, SAID OUTPUT CIRCUIT OF SAID SOLID STATE SWITCHING DEVICE AND SAID PRIMARY WINDING OF SAID IGNITION COIL AND WOUND ON SAID CORE IN A DIRECTION TO DRIVE SAID SATURABLE SWITCHING CORE INTO SAID SECOND STATE OF SATURATION, A THIRD WINDING WOUND ON SAID SATURABLE CORE AND POSITIONED IN THE INPUT CIRCUIT OF SAID SOLID STATE SWITCHING DEVICE, SAID THIRD WINDING WOUND IN A POSITIVE FEEDBACK DIRECTION WITH RESPECT TO SAID SECOND WINDING, AND MEANS FOR PERIODICALLY INTERRUPTING SAID FIRST MENTIONED MEANS FOR PERIODICALLY INTERRUPTING THE COUPLING BETWEEN SAID FIRST WINDING AND SAID SOURCE OF ELECTRICAL ENERGY WHEREBY SAID SOLID STATE SWITCHING DEVICE IS SWITCHED TO ITS CONDUCTING STATE BY THE ENERGY INDUCED IN SAID THIRD WINDING AND IS MAINTAINED IN ITS CONDUCTIVE STATE UNTIL SAID SATURABLE SWITCHING CORE SATURATES IN SAID SECOND DIRECTION WHEREBY SAID PRIMARY WINDING OF SAID IGNITION COIL IS ENERGIZED ONLY DURING THE PERIOD BETWEEN THE INTERRUPTION OF THE COUPLING BETWEEN SAID FIRST WINDING AND SAID SOURCE OF ELECTRICAL ENERGY AND THE SATURATION OF SAID SATURABLE SWITCHING CORE IN SAID SECOND DIRECTION WHICH PERIOD IS SUBSTANTIALLY CONSTANT AND INDEPENDENT OF ENGINE SPEED. 